| 2026 №04 (05) | 2026 №04 (07) |
"Avtomatychne Zvaryuvannya" (Automatic Welding), #4, 2026, pp. 56-64
Influence of focal spot diameter on track formation and melt penetration shape in LPBF-process of 316L steel
S.V. Adzhamskyi1,2
, R.V. Podolskyi1,3,4, T.V. Balakhanova3, O.E. Baranovskaya3, S.I. Badyuk1,4, N.P. Togobytska5
1LLC «Additive Laser Technology of Ukraine». 31v Serhiy Podolynskyi Str., 49000, Dnipro, Ukraine. E-mail: as@alt-print.com
2Institute of Transport Systems and Technologies, NAS of Ukraine. 5 Pysarzhevskyi Str., 49000, Dnipro, Ukraine. E-mail: itst@westa-inter.com
3Z.I. Nekrasov Iron and Steel Institute of the NAS of Ukraine. 1 Akad. Starodubova Squ., 49000, Dnipro, Ukraine. E-mail: rostislavpodolskij@gmail.com
4Institute of Applied Control Systems of the NAS of Ukraine. 42 Akad. Glushkova Ave., 03187, Kyiv, Ukraine. E-mail: IACS@nas.gov.ua
5HTW University of Applied Sciences. 8 Triskovallie Str., 10318, Berlin, Germany. E-mail: Nataliya.Togobytska@htw-berlin.de
СThis study systematically investigates the influence of key laser powder bed fusion (LPBF) process parameters, namely laser spot diameter, laser power, and scanning speed, on the crystallization front geometry of single tracks produced in 316L austenitic stainless steel. Particular attention was paid to evaluating the effect of laser spot diameter. Experimental investigations were performed using a laser processing system equipped with ytterbium fiber lasers featuring a Gaussian beam profile. Single-track experiments were conducted over a wide range of processing conditions, with laser power varying from 150 to 500 W, scanning speed from 700 to 1000 mm/s, and laser spot diameter from 75 to 175 μm. The results demonstrated that the highest track continuity and process stability were achieved with a 75 μm laser spot diameter combined with a laser power of 175…200 W and a scanning speed of 1000 mm/s. Increasing the laser spot diameter beyond 125 μm required a significant increase in laser power to maintain stable melting, accompanied by a noticeable reduction in track stability. At a spot diameter of 175 μm, capillary instability and droplet formation were observed even at high laser power and moderate scanning speeds. Further analysis showed that the optimal melt pool depth-to-width ratio exceeding 0.8, characteristic of the keyhole melting mode, was achieved exclusively with the 75 μm laser spot diameter. In contrast, larger spot diameters produced shallower melt pools, thereby increasing the probability of defect formation in the final components. 21 Ref., 4 Tabl., 8 Fig.
Keywords: LBPF-technology, single track scanning, laser diameter, scanning process parameters
Received: 26.02.2026
Received in revised form: 27.04.2026
Accepted: 20.07.2026
Posted online: 24.07.2026
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